Millimeter wave signals are used for radar and telecommunications. They are also capable of being used to produce data representative of a subject by directing millimeter-wave signals at the subject and detecting the reflected signal. Examples of such imaging systems have been described in U.S. Pat. Nos. 5,455,590; 5,557,283; 5,859,609; 6,507,309; 6,703,964; 6,872,322; and U.S. Patent Application Publication Numbers 2004/0090359, 2004/0140924 and 2006/0066469, which patent references are incorporated herein by reference.